Carburizing steel material of Ring gear and Drive pinion having a high strength and methods for preparing the same

摘要

PURPOSE: A high strength carburized steel product of ring gear and drive pinion is provided which prevents strength deterioration and improves toughness by changing contents of silicon and molybdenum, and improves mechanical properties and forming property only by performing normalizing and air cooling processes, and a method for manufacturing the high strength carburized steel product is provided. CONSTITUTION: The high strength carburized steel product of ring gear and drive pinion comprises 0.13 to 0.20 wt.% of C, 0.06 to 0.15 wt.% of Si, 0.55 to 0.90 wt.% of Mn, 0.03 wt.% or less of P, 0.01 to 0.03 wt.% of S, 0.85 to 1.25 wt.% of Cr, 0.35 to 0.45 wt.% of Mo and a balance of Fe and other inevitable impurities, wherein matrix structure is constructed of a mixed structure of ferrite and bainite. The method for manufacturing the high strength carburized steel product of ring gear and drive pinion comprises the steps of a) heating a composition for the high strength carburized steel product at a temperature of 122020 deg.C for 30 minutes and forging the composition at a temperature of 120030 deg.C for 50 to 55 seconds; and b) heat treating the steel product passing through the forging process in the order of normalizing and air cooling processes, wherein the steel product is air cooled to an ordinary temperature after performing the normalizing process at 960 deg.C for 2 hours.